@ichosethisone 

I've posted several times on successful meshing, but will summarize again in this thread.

Mesh success is mostly dependent on the quality of the radio signal between the root and child AP (for EAP225-outdoor I wouldn't expect solid performance once your signal drops to -82dBm or so (mine run in the -65 to -76 range typically).   I do NOT recommend Auto channel selection for the wired APs if it can be avoided.  Instead I suggest you do a local survey to see what if any channels are in use in your area.  Compare channels in use with which channels you have access to with the highest permitted power output in your region.  Select the best channel and fix your 5.8G radio to this channel on the root node.  For instance, in Canada, ch149 is often a good choice and permits 1W (Wikipedia has a good page on Regions/Channels/Power).  You will also want to avoid DFS-hindered channels if possible (radar avoidance)--almost impossible in the EU.  Leave your child AP on Auto.  In your controller, fix the Child APs preferred uplink AP, which will then appear with a little gold star as of v5.13.  This approach will also minimize reconvergence times in the event of power glitches or other instability.

Physically, do what you can to get clear line of site between the 2 APs that will be meshing, this will maximize the signal strength.  Consider things like height and environmental protection.  One of my favourite locations is a building corner about 18"/50cm down from the soffit level.

Maximize root (wired) nodes and minimize hops and neighbours in the mesh.  I don't recommend more than 3 of either and no more than 6 total, as each mesh link will decrease the overall performance of the mesh.  Disable user access on root nodes when possible on the 5.8G band, consider disabling user access via 5.8G on first hop APs with multiple subtending APs.  Mesh uses a hidden SSID on the 5.8G radios to bridge traffic from wireless nodes back up to the root node, so you don't want all the downstream traffic fighting with local users for radio timeslots if you don't have to.

Use different 5.8ch for root nodes with overlapping coverage areas to avoid poor choices by the software.  Pre-engineer your radio links using the 'preferred uplink' option in the controller--a little sketch goes a long way :)

I use a mix of POE switches and POE injectors and have not had any issues with either.  I have flubbed the occasional outdoor cable connector crimp though and once found a broken conductor in a length of cable I pulled...but super rare.

Monitor your mesh using the Topology feature with Link Labels enable in the controller during different weather (heavy rain, fog, snow, wind).  Set specific alerts for events related to flaky mesh links.  I had a long haul link that worked perfectly fine on a crisp winter day, but became almost unusable with just a few wet leaves appearing in the spring or during a heavy snowfall.

FWIW I find the older EAP225's with external dipole antennae work better for me than the newer outdoor units with integrated PCB antenna, especially for pole mounts.  Your mileage may vary.  

TPlink's mesh tech just works and works really well if you get it set up right.